Process to manufacture 2,3,3,3-tetrafluoropropene

ABSTRACT

Disclosed is a process for the manufacture of 2,3,3,3-tetrafluoropropene comprising: (a) dehydrofluorinating 1,1,1,2,3-pentafluoropropane in the presence of a dehydrofluorination catalyst comprised of chromium (III) oxide, and alkali metal, to produce a product mixture comprising 2,3,3,3-tetrafluoropropene and less than 20 parts per hundred 1,3,3,3-tetrafluoro-1-propene; and (b) recovering said 2,3,3,3-tetrafluoropropene from the product mixture produced in (a).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional application61/183,674, filed Jun. 3, 2009 and U.S. Provisional application61/256,341, filed Oct. 30, 2009.

BACKGROUND INFORMATION

1. Field of the Disclosure

This disclosure relates in general to methods of synthesis offluorinated olefins.

2. Description of the Related Art

The fluorocarbon industry has been working for the past few decades tofind replacement refrigerants for the ozone depletingchlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) beingphased out as a result of the Montreal Protocol. The solution for manyapplications has been the commercialization of hydrofluorocarbon (HFC)compounds for use as refrigerants, solvents, fire extinguishing agents,blowing agents and propellants. These new compounds, such as HFCrefrigerants, HFC-134a and HFC-125 being the most widely used at thistime, have zero ozone depletion potential and thus are not affected bythe current regulatory phase-out as a result of the Montreal Protocol.

In addition to ozone depleting concerns, global warming is anotherenvironmental concern in many of these applications. Thus, there is aneed for compositions that meet both low ozone depletion standards aswell as having low global warming potentials. Certain hydrofluoroolefinsare believed to meet both goals. Thus there is a need for manufacturingprocesses that provide halogenated hydrocarbons and fluoroolefins thatcontain no chlorine that also have a low global warming potential. Thereis also considerable interest in developing new refrigerants withreduced global warming potential for the mobile air-conditioning market.

HFC-1234yf (CF₃CF═CH₂) and HFC-1234ze (CF₃CH═CHF), both having zeroozone depletion and low global warming potential, have been identifiedas potential refrigerants. U.S. Patent Publication No. 2006/0106263 A1discloses the production of HFC-1234yf by a catalytic vapor phasedehydrofluorination of CF₃CF₂CH₃ or CF₃CHFCH₂F, and of HFC-1234ze(mixture of E- and Z-isomers) by a catalytic vapor phasedehydrofluorination of CF₃CH₂CHF₂.

There is a continuing need for more selective and efficientmanufacturing processes for the production of HFC-1234yf

SUMMARY

In one aspect, disclosed is a process for the manufacture of2,3,3,3-tetrafluoropropene comprising: dehydrofluorinating1,1,1,2,3-pentafluoropropane in the presence of a dehydrofluorinationcatalyst comprised of chromium (III) oxide, and alkali metal, to producea product mixture comprising 2,3,3,3-tetrafluoropropene; and recoveringsaid 2,3,3,3-tetrafluoropropene from the product mixture produced in thedehydrofluorination.

The foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of theinvention, as defined in the appended claims.

DETAILED DESCRIPTION

In one aspect, disclosed is a process for the manufacture of2,3,3,3-tetrafluoropropene comprising: dehydrofluorinating1,1,1,2,3-pentafluoropropane in the presence of a dehydrofluorinationcatalyst comprised of chromium (III) oxide, and alkali metal, to producea product mixture comprising 2,3,3,3-tetrafluoropropene; and recoveringsaid 2,3,3,3-tetrafluoropropene from the product mixture produced in thedehydrofluorination. In one embodiment, the product mixture comprising2,3,3,3-tetrafluoropropene further comprises less than 20 parts perhundred on a molar basis of 1,1,1,2,2-pentafluoropropane. In anotherembodiment, the product mixture comprising 2,3,3,3-tetrafluoropropenefurther comprises less than 10 parts per hundred on a molar basis of1,1,1,2,2-pentafluoropropane. In one embodiment, the dehydrofluorinationcatalyst comprises chromium (III) oxide and at least 1000 ppm alkalimetal. In another embodiment, the dehydrofluorination catalyst compriseschromium (III) oxide and at least 3000 ppm alkali metal. In yet anotherembodiment, the dehydrofluorination catalyst comprises chromium oxideand at least 5000 ppm alkai metal. In yet another embodiment, thedehydrofluorination catalyst comprises chromium oxide and at least 1000ppm potassium. In yet another embodiment, In another embodiment, thedehydrofluorination catalyst comprises from 0.1% to 3% boron and atleast 3000 ppm of alkali metal. In another embodiment, thedehydrofluorination catalyst comprises from 0.5% to 2% boron and atleast 3000 ppm of alkali metal. In yet another embodiment, thedehydrofluorination catalyst comprises from 0.5% to 2% boron and atleast 3000 ppm of sodium. In yet another embodiment, thedehydrofluorination catalyst comprises from 0.5% to 2% boron and atleast 2000 ppm of potassium.

Many aspects and embodiments have been described above and are merelyexemplary and not limiting. After reading this specification, skilledartisans appreciate that other aspects and embodiments are possiblewithout departing from the scope of the invention.

Other features and benefits of any one or more of the embodiments willbe apparent from the following detailed description, and from the claims

Before addressing details of embodiments described below, some terms aredefined or clarified.

The catalytic dehydrofluorination of hydrofluorocarbons to producehydrofluoroolefins is ordinarily carried out in the vapor phase using adehydrofluorination catalyst. Vapor phase dehydrofluorination catalystsare well known in the art. These catalysts include, but are not limitedto, alumina, aluminum fluoride, fluorided alumina, metal compounds onaluminum fluoride, metal compounds on fluorided alumina; chromiumoxides, fluorided chromium oxides, and cubic chromium trifluoride;oxides, fluorides, and oxyfluorides of magnesium, zinc and mixtures ofmagnesium and zinc and/or aluminum; lanthanum oxide and fluoridedlanthanum oxide; carbon, acid-washed carbon, activated carbon, threedimensional matrix carbonaceous materials; and metal compounds supportedon carbon. The metal compounds are oxides, fluorides, and oxyfluoridesof at least one metal selected from the group consisting of sodium,potassium, rubidium, cesium, yttrium, lanthanum, cerium, praseodymium,neodymium, samarium, chromium, iron, cobalt, rhodium, nickel, copper,zinc, and mixtures thereof.

In the preparation of HFC-1234yf by dehydrofluorination of CF₃CHFCH₂F,it is possible to obtain either HFC-1234yf or HFC-1234ze, depending onwhich pair of adjacent fluorine and hydrogen atoms are eliminated.Generally, HFC-1234yf is the predominant product, although depending onreaction conditions, yields of HFC-1234ze can be as much 10 pph or morecompared to HFC-1234yf. It has also been found that another by-productof the catalytic dehydrofluorination of CF₃CHFCH₂F (HFC-245eb) isCF₃CF₂CH₃ (HFC-245cb) which can be very difficult to separate fromHFC-1234yf. This product is believed to arise via the re-addition ofhydrogen fluoride to HFC-1234yf in the direction opposite to that it waseliminated by. Although HFC-245cb can be catalyticallydehydrofluorinated to HFC-1234yf, in practice the dehydrofluorination ofHFC-245cb requires higher temperatures and a different catalyst.Depending upon the catalyst and reaction conditions, the amount ofHFC-245cb produced by isomerization can be as much as from 30 to 60parts per hundred of HFC-1234yf, resulting in significant yield losses.Selectivity for the production of HFC-1234yf can be expressed as partsper hundred of the by-product relative to the amount of HFC-1234yf. Byway of example, a product mixture formed from the dehydrofluorination ofHFC-245eb comprising 60% HFC-1234yf, 20% HFC-245cb and 3% HFC-1234zewould have 33 pph HFC-245cb and 5 pph HFC-1234ze.

It is possible to dehydrofluorinate CF₃CHFCH₂F (HFC-245eb) to HFC-1234yfwith high selectivity and very little formation of HFC-245cb using acatalyst comprising chromium (III) oxide, and alkali metal. In oneembodiment, the alkali metal is at least one of sodium, potassium andcesium, or mixtures thereof.

In one embodiment, the catalyst comprises chromium (III) oxide, and anamount of alkali metal effective to produce2,3,3,3-tetrafluoro-1-propene while producing less than 20 pph or1,1,1,2,2-pentafluoropropane. The effective amount of alkali metalrequired will be dependent upon how it is distributed within thecatalyst composition. The effective amount of alkali metal required isalso dependent on which alkali metal is chosen. An effective amount ofcesium is less than an effective amount of potassium, which is less thanan effective amount of sodium.

In one embodiment, the dehydrofluorination catalyst comprises chromium(III) oxide and at least 1000 ppm alkali metal. In another embodiment,the dehydrofluorination catalyst comprises chromium (III) oxide and atleast 3000 ppm alkali metal. In yet another embodiment, thedehydrofluorination catalyst comprises chromium oxide and at least 5000ppm alkai metal. In yet another embodiment, the dehydrofluorinationcatalyst comprises chromium oxide and at least 1000 ppm potassium. Inanother embodiment, the dehydrofluorination catalyst comprises from 0.1%to 3% boron and at least 3000 ppm of alkali metal. In anotherembodiment, the dehydrofluorination catalyst comprises from 0.5% to 2%boron and at least 3000 ppm of alkali metal. In yet another embodiment,the dehydrofluorination catalyst comprises from 0.5% to 2% boron and atleast 3000 ppm of sodium. In yet another embodiment, the catalystcomprises chromium (III) oxide, from 0.5% to 2% boron, and at least 2000ppm potassium. In one embodiment, the catalyst is a chromium compositionknown as Guignet's green pigment.

In one embodiment, the dehydrofluorination catalyst may be prepared byslurrying preformed pellets or particles of chromium (III) oxidecatalyst in an aqueous solution of an alkali metal salt, such as sodiumcarbonate, potassium carbonate or cesium carbonate. The slurry is thenallowed to dry.

In another embodiment, the dehydrofluorination catalyst may be preparedby slurring chromium (III) oxide powder with an aqueous solution of analkali metal salt, such as sodium carbonate, potassium carbonate orcesium carbonate. The slurry is then allowed to dry. In one embodiment,the dehydrofluorination catalyst is then pressed, ground into particles,and sieved to 12/20 mesh particles

In yet another embodiment, the catalyst may be prepared by fusing amixture of from 3 parts to 16 parts boric acid and 1 part potassiumdichromate at from 500-800° C., cooling the mixture in air, crushing thesolid to produce a powder, hydrolysis, filtering, drying, milling andscreening. Numerous, examples of the preparation of Guignet's green canbe found in the art, including U.S. Pat. No. 3,413,363, the disclosureof which is herein incorporated by reference.

The physical shape of the catalyst is not critical and may, for example,include pellets, powders or granules.

In one embodiment, the catalytic dehydrofluorination may be suitablyconducted with the temperature set point of the reactor in the range offrom about 250° C. to about 350° C. In another embodiment, the catalyticdehydrofluorination is conducted with the temperature set point of thereactor in the range of from about 250° C. to about 300° C. In oneembodiment, the contact time is typically from about 1 to about 450seconds. In another embodiment, the contact time is from about 10 toabout 120 seconds.

The reaction pressure can be subatmospheric, atmospheric orsuperatmostpheric. Generally, near atmospheric pressures are preferred.However, the dehydrofluorination can be beneficially run under reducedpressure (i.e., pressures less than one atmosphere).

In one embodiment, the catalytic dehydrofluorination is carried out inthe presence of an inert gas such as nitrogen, helium, or argon. Theaddition of an inert gas can be used to increase the extent ofdehydrofluorination. Of note are processes where the mole ratio of inertgas to hydrofluorocarbon undergoing dehydrofluorination is from about5:1 to about 0.5:1. In one embodiment, nitrogen is the inert gas.

Reaction product HFC-1234yf and any unconverted HFC-245eb are recoveredfrom the effluent leaving the reactor. The unconverted HFC-245eb can berecycled back to the reactor to produce additional HFC-1234yf. In oneembodiment of this invention, the unconverted HFC-245eb is recycled backto the reactor as it's azeotrope with HF. Published PCT Application WO2008/002501 filed Jun. 27, 2006 and, disclosing an azeotrope ofHF/HFC-245eb, is incorporated herein in its entirety. U.S. Pat. No.7,423,188 discloses an azeotrope of the E-isomer of HFC-1234ze and HFand a method to separate the HFC-1234ze from the azeotrope, and U.S.Pat. No. 7,476,771 discloses an azeotrope of HFC-1234yf and HF and amethod to separate the HFC-1234yf from the azeotrope. HFC-1234ze may berecovered as a HF/HFC-1234ze azeotrope. Similarly, HFC-1234yf may berecovered as a HF/HFC-1234yf azeotrope. Pure HFC-1234ze and pureHFC-1234yf can be further recovered from their HF azeotropes by usingmethods similar to those described in U.S. Pat. No. 7,423,188 and U.S.Pat. No. 7,476,771, and both of which are incorporated herein byreference.

The reactor, or reactor bed, distillation columns, and their associatedfeed lines, effluent lines, and associated units used in applying theprocesses of this invention should be constructed of materials resistantto hydrogen fluoride. Typical materials of construction, well-known tothe fluorination art, include stainless steels, in particular of theaustenitic type, the well-known high nickel alloys, such as Monel™nickel-copper alloys, Hastelloy™ nickel-based alloys and, Inconel™nickel-chromium alloys, and copper-clad steel.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of “a” or “an” are employed to describe elements andcomponents described herein. This is done merely for convenience and togive a general sense of the scope of the invention. This descriptionshould be read to include one or at least one and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Group numbers corresponding to columns within the Periodic Table of theelements use the “New Notation” convention as seen in the CRC Handbookof Chemistry and Physics, 81^(st) Edition (2000-2001).

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present invention, suitablemethods and materials are described below. All publications, patentapplications, patents, and other references mentioned herein areincorporated by reference in their entirety, unless a particular passageis cited. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

EXAMPLES

The concepts described herein will be further described in the followingexamples, which do not limit the scope of the invention described in theclaims.

In the examples the follow abbreviations or codes may be used:

CT=contact time

1234yf ═CF₃CF═CH₂ 245eb ═CF₃CHFCH₂F 1234ze ═CF₃CH═CHF 245cb ═CF₃CF₂CH₂Example 1

Example 1 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over a chromium oxide catalyst furthercomprising boron, potassium and sodium.

An inconel tube (⅝ inch OD) was filled with 6 cc (4.9 gm) of hydratedchromic oxide (also known as Guignet's Green) in extrudate form, whichwas crushed and sieved to 12/20 mesh. A typical analysis of thiscatalyst indicated the following composition: 54.5% Cr, 1.43% B, 3400ppm Na, 120 ppm K. The temperature of the catalyst bed was raised to325° C. and purged with nitrogen (38 sccm, 6.3×10⁻⁷ m³/sec) for 120minutes and then at 300° C. for 80 minutes. Then the flow of nitrogenwas reduced to 27 sccm (4.5×10⁻⁷ m³/sec) and HF was fed at 9 sccm(1.5×10⁻⁷ m³/sec) for 500 minutes. The flow of nitrogen was then loweredto 19 sccm (3.2×10⁻⁷ m³/sec) and the flow of HF was raised to 15 sccm(2.5×10⁻⁷ m³/sec) for 25 minutes. The flow of nitrogen was then loweredto 11 sccm (1.8×10⁻⁷ m³/sec) and the flow of HF was raised to 21 sccm(3.5×10⁻⁷ m³/sec) for 30 minutes. The flow of nitrogen was then loweredto 4 sccm (6.7×10⁻⁸ m³/sec) and the flow of HF was raised to 27 sccm(4.5×10⁻⁷ m³/sec) for 30 minutes. The flow of nitrogen was thendiscontinued and the flow of HF was raised to 30 sccm (5.0×10⁻⁷ m³/sec)for 160 minutes. After this activation period, the catalyst bedtemperature was changed to reaction conditions.

The reactor temperature was stabilized at temperatures from 250° C. to302° C., as indicated in the table below, and CF₃CHFCH₂F was fed at 6.4sccm (1.1×10⁻⁷ m³/sec). The CF₃CHFCH₂F was vaporized at 41° C. whilepassing nitrogen through the vaporizer at 6.4 sccm (1.1×10⁻⁷ m³/sec).Part of the reactor effluent was passed through a series of valves andanalyzed by GCMS. The results in Table 1 are an average of at least twoGC injections at each set of conditions. Amounts for 245 cb and 1234zeare expressed as mole parts per hundred of 2,3,3,3-tetrafluoropropeneproduced.

TABLE 1 Mole % 245cb 1234ze 245eb Temp CT 1234yf (pph) (pph) (%) ° C.(sec) 71.7 8.9 5.2 17.5 302 28 47.9 6.1 4.0 46.6 275 28 28.9 4.5 2.868.4 250 28

Example 2

Example 2 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over chromium oxide catalysts furthercomprising varying amounts of boron, potassium and sodium.

An inconel tube (½ inch OD) was filled with 6 cc (4.9 gm) of hydratedchromic oxide in extrudate form, which was crushed and sieved to 12/20mesh. Composition of the catalysts with respect to B, Na and K are asindicated in Table 2. The temperature of the catalyst bed was raised to300° C. and purged with nitrogen (30 cc/min) for 200 minutes. Then theflow of nitrogen was reduced to 60 cc/min and HF was fed at 20 cc/minfor 60 minutes. The temperature was increase to 325° C. for 300 minutes.The flow of nitrogen was then lowered to 30 cc/min and the flow of HFwas raised to 30 cc/min for 30 minutes. The flow of nitrogen was thenlowered to 12 cc/min and the flow of HF was raised to 48 cc/min for 60minutes. The flow of nitrogen was then discontinued and the flow of HFwas raised to 48 cc/min for 30 minutes. The reactor temperature was thendecreased to 250° C. for 30 minutes. Afterwards HF was turned off andthe reactor was purged with 30 cc/min of nitrogen. The reactortemperature was then stabilized at 300° C., the flow of nitrogen wasturned off, and CF₃CHFCH₂F was fed at 3.2 ml/hr (12 cc/min). TheCF₃CHFCH₂F was vaporized at 175° C. Part of the reactor effluent waspassed through a series of valves and analyzed by GCMS. Amounts for 245cb and 1234ze are expressed as mole parts per hundred of2,3,3,3-tetrafluoropropene produced.

TABLE 2 % Na K Mole % 245cb 1234ze 245eb Temp CT B ppm ppm 1234yf (pph)(pph) (%) ° C. (sec) 1.1 3225 135 58.1 28.5 2.7 23.20 300 30 1.6 4917000 53.7 10.0 2 39.2 300 30 1.6 4550 150 52.8 15.5 2.9 36.68 300 30

Example 3

Example 3 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over chromium oxide catalysts furthercomprising varying amounts of added potassium.

Chromium oxide catalyst which had a starting composition of 55.8% Cr,175 ppm Na, 60 ppm K, 53 ppm Cu and 20 ppm Zn was doped with varyinglevels of potassium. Composition of the catalysts with respect to amountof K added is indicated in Table 3.

An inconel tube (½ inch OD) was filled with 6 cc (4.9 gm) of catalystwhich had been prepared as follows. Hydrated chromic oxide in extrudateform, which was crushed and sieved to 12/20 mesh was doped with varyinglevels of potassium by slurring catalyst with an aqueous potassiumcarbonate solution containing enough potassium to provide the indicatedpotassium levels. The solution was then evaporate to dryness, and theresulting catalyst was dried at 200° C. for 3 hours. After charging thereactor tube, the temperature of the catalyst bed was raised to 300° C.and purged with nitrogen (30 cc/min) for 200 minutes. Then the flow ofnitrogen was reduced to 60 cc/min and HF was fed at 20 cc/min for 60minutes. The temperature was increase to 325° C. for 300 minutes. Theflow of nitrogen was then lowered to 30 cc/min and the flow of HF wasraised to 30 cc/min for 30 minutes. The flow of nitrogen was thenlowered to 12 cc/min and the flow of HF was raised to 48 cc/min for 60minutes. The flow of nitrogen was then discontinued and the flow of HFwas raised to 48 cc/min for 30 minutes. The reactor temperature was thendecreased to 250° C. for 30 minutes. Afterwards HF was turned off andthe reactor was purged with 30 cc/min of nitrogen. The reactortemperature was then stabilized at 300° C., the flow of nitrogen wasturned off, and CF₃CHFCH₂F was fed at 3.2 ml/hr (12 cc/min). TheCF₃CHFCH₂F was vaporized at 175° C. Part of the reactor effluent waspassed through a series of valves and analyzed by GCMS. Amounts for245cb and 1234ze are expressed as mole parts per hundred of2,3,3,3-tetrafluoropropene produced.

TABLE 3 K added - 1234ze 245eb 1234yf 245cb ppm (pph) (%) (%) (pph) 10012.97 9.73 31.01 45.60 5000 5.30 11.83 73.4 9.47 6500 3.87 34.7 58.552.88 10000 0.73 82.41 16.52 0

Example 4

Example 3 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over a gamma alumina dehydrofluorinationcatalyst.

A batch of gamma alumina (BASF) (6 cc, 3.19 gm) was activated as thecatalyst in Example 1 described above. The temperature of the reactorwas controlled temperatures from 249° C. to 299° C., as indicated in thetable below, and CF₃CHFCH₂F was fed at 6.4 sccm (1.1×10⁻⁷ m³/sec). TheCF₃CHFCH₂F was vaporized at 41° C. while passing nitrogen through thevaporizer at 6.4 sccm (1.1×10⁻⁷ m³/sec). Part of the reactor effluentwas passed through a series of valves and analyzed by GCMS. The resultsin Table 4 are an average of at least two GC injections at each set ofconditions. Amounts for 245 cb and 1234ze are expressed as mole partsper hundred of 2,3,3,3-tetrafluoropropene produced.

TABLE 4 Mole % 245cb 1234ze 245eb Temp CT 1234yf (pph) (pph) (%) ° C.(sec) 68.7 32.5 8.0 2.9 299 28 64.4 43.3 6.1 3.3 276 28 57.3 46.9 3.313.5 249 28

Example 5

Example 5 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over an alpha chromium oxide catalyst.

A batch of alpha chromium oxide (6 cc, 8.51 gm) as described in U.S.Pat. No. 5,036,036 was activated as the catalyst in Example 1 describedabove. Analysis of the catalyst indicated the following composition:55.8% Cr, 0% B, 175 ppm Na, 60 ppm K. The temperature of the reactor wascontrolled temperatures from 249° C. to 298° C., as indicated in thetable below, and CF₃CHFCH₂F was fed at 6.4 sccm (1.1×10⁻⁷ m³/sec). TheCF₃CHClCH₂CCl₂CF₃ was vaporized at 41° C. while passing nitrogen throughthe vaporizer at 5.4 sccm (9.5×10⁻⁸ m³/sec). Part of the reactoreffluent was passed through a series of valves and analyzed by GCMS. Theresults in Table 5 are an average of at least two GC injections at eachset of conditions. Amounts for 245 cb and 1234ze are expressed as moleparts per hundred of 2,3,3,3-tetrafluoropropene produced.

Analysis of the alpha chromium oxide catalyst indicated it comprised55.8% chromium, 53 ppm copper, 120 ppm iron, 175 ppm sodium, 60 ppmpotassium, 23 ppm manganese, and 20 ppm zinc.

TABLE 5 Mole % 245cb 1234ze 245eb Temp CT 1234yf (pph) (pph) (%) ° C.(sec) 65.5 34.5 11 4.1 298 31 61.8 46.3 8.1 4.1 277 31 57.7 59.4 5.2 4.6249 31

Example 6

Example 6 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over an chromium oxide gel catalyst.

A batch of chromium oxide gel (6 cc, 7.47 gm) obtained from BASF wasactivated as the catalyst in Example 1 described above. The temperatureof the reactor was controlled temperatures from 249° C. to 298° C., asindicated in the table below, and CF₃CHFCH₂F was fed at 6.4 sccm(1.1×10⁻⁷ m³/sec). The CF₃CHClCH₂CCl₂CF₃ was vaporized at 41° C. whilepassing nitrogen through the vaporizer at 5.4 sccm (9.5×10⁻⁸ m³/sec).Part of the reactor effluent was passed through a series of valves andanalyzed by GCMS. The results in Table 6 are an average of at least twoGC injections at each set of conditions. Amounts for 245 cb and 1234zeare expressed as mole parts per hundred of 2,3,3,3-tetrafluoropropeneproduced.

TABLE 6 Mole % 245cb 1234ze 245eb Temp CT 1234yf (pph) (pph) (%) ° C.(sec) 69.0 33.9 6.4 1.8 299 31 64.4 47.0 4.0 1.5 277 31 59.5 63.4 1.50.9 248 31

Example 7

Example 7 demonstrates the dehydrofluorination of1,1,1,2,3-pentafluoropropane over an chromium oxide gel catalyst.

A batch of chromium oxide gel (6 cc, 5.9 gm) obtained from Synetix(CPA200A) was activated as the catalyst in Example 1 described above.The temperature of the reactor was controlled temperatures from 251° C.to 301° C., as indicated in the table below, and CF₃CHFCH₂F was fed at6.4 sccm (1.1×10⁻⁷ m³/sec). The CF₃CHClCH₂CCl₂CF₃ was vaporized at 41°C. while passing nitrogen through the vaporizer at 5.4 sccm (9.5×10⁻⁸m³/sec). Part of the reactor effluent was passed through a series ofvalves and analyzed by GCMS. The results in Table 7 are an average of atleast two GC injections at each set of conditions. Amounts for 245 cband 1234ze are expressed as mole parts per hundred of2,3,3,3-tetrafluoropropene produced.

Analysis of the chromium oxide gel catalyst indicated it comprised 62.9%chromium, 350 ppm copper, 198 ppm sodium, 145 ppm iron and 50 ppmpotassium.

TABLE 7 Mole % 245cb 1234ze 245eb Temp CT 1234yf (pph) (pph) (%) ° C.(sec) 70.8 30.5 6.2 1.8 301 31 65.9 43.6 3.9 1.5 276 31 67.3 42.6 1.91.3 251 31

Note that not all of the activities described above in the generaldescription or the examples are required, that a portion of a specificactivity may not be required, and that one or more further activitiesmay be performed in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed.

In the foregoing specification, the concepts have been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofinvention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

It is to be appreciated that certain features are, for clarity,described herein in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any subcombination.Further, reference to values stated in ranges include each and everyvalue within that range.

1. A process for the manufacture of 2,3,3,3-tetrafluoropropenecomprising: (a) dehydrofluorinating 1,1,1,2,3-pentafluoropropane in thepresence of a dehydrofluorination catalyst comprised of chromium (III)oxide, and an alkali metal in an amount effective to produce a productmixture comprising 2,3,3,3-tetrafluoropropene and less than 20 parts perhundred of 1,1,1,2,2-pentafluoropropane; and (b) recovering said2,3,3,3-tetrafluoropropene from the product mixture produced in (a). 2.A process of claim 1, wherein said product mixture comprising2,3,3,3-tetrafluoropropene comprises less than 10 parts per hundred on amolar basis of 1,1,1,2,2-pentafluoropropane.
 3. The process of claim 1,wherein said dehydrofluorination catalyst comprises from 0.1% to 2%alkali metal disposed on the surface of said catalyst.
 4. The process ofclaim 1, wherein said dehydrofluorination catalyst comprises from 0.1%to 1% alkali metal disposed on the surface of said catalyst.
 5. Theprocess of claim 1, wherein said dehydrofluorination catalyst comprisesfrom 0.1% to 1% potassium disposed on the surface of said catalyst. 6.The process of claim 1, wherein said dehydrofluorination catalystcomprises from 0.5% to 2% alkali metal dispersed throughout theparticles of said catalyst.
 7. The process of claim 1, wherein saiddehydrofluorination catalyst comprises from 0.1% to 3% boron and atleast 3000 ppm of alkali metal.
 8. The process of claim 1, wherein saiddehydrofluorination catalyst comprises from 0.5% to 2% boron and atleast 3000 ppm of sodium.
 9. The process of claim 1, wherein saiddehydrofluorination catalyst comprises from 0.55 to 2% boron and atleast 1000 ppm potassium.
 10. The process of claim 1, wherein thetemperature of the catalyst is maintained at a set point of from 250° C.to 350° C.
 11. The process of claim 8, wherein the temperature of thecatalyst is maintained at a set point of from 250° C. to 300° C.